The invention relates to an insertion post for transferring the location and orientation of at least one implant introduced in a jaw of a patient onto a model.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Patients who lost one or several teeth have nowadays various options to replace a lost tooth with a tooth replacement or artificial tooth. In addition to bridges which involve a tooth replacement mounted for example between still existing teeth, there are implants for providing adequate dental restoration. The implant is screwed in the position of the missing tooth into the jaw of the patient and has an abutment which is inserted in the implant to support the artificial tooth in form of a crown. The artificial tooth is provided in many cases not only for reasons of aesthetic. Medical criteria also are oftentimes relevant. When teeth are missing, the jaw may shift or shrink, and bones may degrade during the course of time in the absence of suitable restoration. In addition, teeth in the opposite jaw have no longer a counterpart and may extract from the jaw, causing further tooth loss.
To model the tooth replacement, typically a crown, the tooth or mouth structure of the patient is transferred to a master model. The mouth structure includes hereby the contours of the still existing teeth and also the position or location and orientation of the implants mounted in the bone. The orientation is hereby realized by indexing which typically is implemented in the implant by a rotationally restrained interface, oftentimes as hexagon socket. The abutment includes further an insert piece which provides with the implant a connection which is restrained against rotation. When the abutment and the crown are fabricated, it can be ensured in this way that the crown, when inserted, is correctly oriented and as envisioned in the model fits in the still existing tooth structure of the patient.
For transfer of the location and orientation of the implant, application of the closed and open tray techniques is known. In either technique, the mouth structure is transferred onto a model with the aid of impression material and impression posts that are inserted in the corresponding implant. An impression post for the open tray technique normally has an insertion post and a fixation element formed as a screw for fastening the insertion post to the implant. In the open tray technique, the insertion posts remain in the impression material, when removing the impression tray from the mouth. For this purpose, the fixation elements are loosened before removal of the impression tray. This is made possible by providing in the impression tray holes through which the fixation elements can be guided for loosening the insertion posts from the implants.
The provision of an impression is especially difficult when several substantially angled or pairs of skewed, non parallel, implants are involved simultaneously. As a result of the inevitable undercut of the connection to the implant, a kind of interlocking of the implants with one another is encountered because of the viscosity of the impression material. Impression of a group of interlocked implants is possible only in opposition to the substantially elastic resistance of the impression material. In other words, during removal of the impression material from the mouth, the impression material is deformed in some areas. In practice, impression materials do not behave completely elastic, so that the deformation is not completely reversed. This may lead to a substantial rebound inaccuracy of the impression material, potentially causing inaccuracies of the impression. The resistance of the impression material and the undercut of the connections to the individual implants may also cause uncomfort for the patient because the impression tray can be detached from the jaw only with increased force application.
It would therefore be desirable and advantageous to address these problems and to obviate other prior art shortcomings.